05 Glossary

Anthropogenic climate change/global warming

During the period of industrialisation, greenhouse gas emissions increased steadily and led to an atmospheric CO2 concentration of 380 ppm in 2004. The pre-industrial level was 280 to 300 ppm which at least for the past 650,000 years and probably for the last millions of years has not been exceeded. There are other greenhouse gases such as methane or dinitrogen oxide, which have increased equally fast.

Greenhouse gases alter the radiation properties of the atmosphere in such a way that much more energy from the sun is trapped by the lower parts of the atmosphere. This anthropogenic global warming comes in addition to what is called the natural greenhouse effect. Even before the appearance of mankind and of the industrial age the earth's atmosphere contained greenhouse gases (in particular CO2 and others), which have warmed the earth's surface by roughly 33°C. This natural greenhouse effect must be regarded as a precondition for the development of life on the planet.

Tropical cyclone

General expression for tropical storms forming over tropical oceans. Depending on the region and strength they are called hurricanes (Atlantic and Northeast Pacific), typhoons (Northwest Pacific), or cyclones (Indian Ocean and Australia).

Saffir-Simpson intensity scale

The Saffir-Simpson Scale is a five-stage intensity scale for tropical cyclones. The scale spans the following categories:

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  Cat 1: windspeed 118—153 km/h; central pressure >= 980 hPa
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  Cat 2: windspeed 154—177 km/h; central pressure 965—979 hPa
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  Cat 3: windspeed 178—209 km/h; central pressure 945—964 hPa
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  Cat 4: windspeed 210—249 km/h; central pressure 920—944 hPa
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  Cat 5: windspeed > 250 km/h; central pressure < 920 hPa

Atlantic cold phases/warm phases

The so-called cold and warm phases in the North Atlantic are part of the Atlantic Multidecadal Oscillation (AMO). The mechanism behind it is a large-scale water flow conveyer belt in the ocean with periodically enhanced or reduced activity resulting in unusually warm or unusually cool surface waters in parts of the ocean. This overturning circulation, which is driven by water temperatures and water salinities, is called the thermohaline circulation.

Natural climate oscillation

Natural climate oscillations can be differentiated by the respective time scales. They are not driven by external influences on the earth's climate system, such as changes in solar irradiance or anthropogenic greenhouse gas emissions. Examples of natural climate oscillations are the El-Nino/Southern-Oscillation events (interdecadal time scale), the North Atlantic Oscillation (quasi-decadal Oscillation) or the Atlantic Multidecadal Oscillation (multidecadal time scale).